Abstract
Recently, a new kind of distributed element superconducting resonators with granular aluminum (grAl) has been developed for circuit quantum electrodynamics. Given that lumped element resonators possess certain advantages over the distributed element ones, in this paper, we use a relatively simple micro-nanotechnology, without the etching process, to fabricate the designed lumped element superconducting grAl resonators. They are deposited on silicon substrates by DC magnetron sputtering of pure Al in an atmosphere of Ar and O2. By cryogenic microwave transmission measurements, at a temperature of 50 mK, we find that, compared with a usual Al resonator of the same size, such a device shows significantly strong nonlinearity and thus higher kinetic inductance. The noise features, quality factors, and temperature-dependence of the resonant frequencies have been investigated experimentally. It is believed that the lumped element superconducting resonators with high kinetic inductance demonstrated here could also be applied to superconducting quantum computation and photon counting in the future.
Highlights
The tested sample is diced into 5 × 10 mm2 wafers, which are stuck to a copper box using low temperature glue and wire-bonded to a printed circuit board (PCB) with a characteristic impedance of 50 Ω
The microwave transport measurements of the fabricated resonators, at low temperature, mainly include two parts, schematically shown in Fig. 2; the S21-parameter is measured by the vector network analyzer (VNA), and the noise features of the devices are tested by the IQ-mixer technique
The resonant frequency of the first granular aluminum (grAl) resonator is measured as f
Summary
The microwave transport measurements of the fabricated resonators, at low temperature, mainly include two parts, schematically shown in Fig. 2; the S21-parameter is measured by the vector network analyzer (VNA), and the noise features of the devices are tested by the IQ-mixer technique.21,22 The Al sample and the grAl one are individually measured. By comparing the measured resonant frequency with that obtained by the finite element method simulation, we extract a sheet kinetic inductance LgkrinAeltic = 20 pH/◻.
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